Control systems for hydraulically operated elements circuits or systems

Abstract

Method of controlling two separately operable hydraulic circuits involving monitoring the pressure conditions in one of the circuits, comparing this pressure with a reference pressure which is established in the control system to produce a first error signal which is used to correct if necessary the pressure within the one circuit. Performing the same operation in the case of the second circuit using the same reference pressure. In particular the system and apparatus of the invention is used for controlling the tensions in the warps of a trawl automatically throughout the shooting, trawling and hauling-in of a trawl.

I claim: 
     
       1. A control system for controlling hydraulically operated winch assemblies whose cables, wires or the like are intended to be connected with the same trawl or other form of net used for sea fishing or for use with other objects or in situations in which it is required to maintain predetermined tensions in the cables, wires or the like, the control system including means for enabling a number of reference pressure levels each indicative of a particular required operational condition for the cables, wires or the like; such as paying-out, continuous pull, hauling-in; separate means for monitoring the operational conditions of the winch assemblies; means for comparing the results of the monitoring with an associated one of said reference pressure levels thereby to provide associated operational condition indication signals; and control means so responsive to such signals as to cause independent corresponding variation of the operational conditions of the relevant winch assembly; said control system further comprising interference response means responsive to interference to a required movement of the common object, the interference responsive means including means for enabling paying-out of a predetermined additional length of cables, wires or the like; means for detecting whether the interference still persists following the pay-out of the additional length of the cables, wires or the like and for arresting any such additional pay-out thereby to permit the tension conditions in the cables, wires or the like to increase to a predetermined higher level to enable application of increased force on the object connected thereto for the purposes of attempting forcibly to free the said object from the interference; and means for causing adjustment of the control means to allow further paying-out of the cable, wire or the like if said interference still persists so as to prevent said higher level being exceeded, and to provide an alarm signal indicative that the predetermined higher level had been attained and that the interference still persists. 
     
     
       2. A control system as claimed in claim 1, and including means for enabling manual adjustment and operation of the control means for the purposes of varying the operational conditions of the hydraulic winch assemblies; and means for enabling automatic changeover between manual and non-manual operation when the amount of cable; wire or the like payed-out is not greater than a preselectable amount. 
     
     
       3. A control system as claimed in claim 1, and in which said reference pressure levels include one characteristic of a predetermined difference in the lengths of cables, wires or the like payed-out by the winch assemblies, and in which means are provided for producing a signal related to the actual difference in the amounts of cables, wires or the like payed-out; said control means being so responsive to the length difference reference level and said actual length difference as to produce an alarm or other indication of the condition that the amount of the cables payed-out by the winch assemblies has exceeded a predetermined level. 
     
     
       4. A control system as claimed in claim 1, in which a control and information display unit is adapted to enable presetting of said selectively variable reference values and display of the operational state of the control system; a pressure control sequency unit enables comparison of the presettable reference pressure levels with the instantanious values of the said winch assembly operational conditions; and a microprocessor unit enables inter-relating presettable and instantaneous values of the lengths, cables, wires or the like and tensions with the corresponding reference levels. 
     
     
       5. A control system for controlling hydraulically operated winch assemblies whose cables, wires or the like are intended to be connected with the same trawl or other form of net used for sea fishing or for use with other objects or in situations in which it is required to maintain predetermined tensions in the cables, wires or the like, the control system including means for enabling a number of reference pressure levels each indicative of a particular required operational condition for the cables, wires or the like; such as paying-out, continuous pull, hauling-in; separate means for monitoring the operational conditions of the winch assemblies; means for comparing the results of the monitoring with an associated one of said reference pressure levels thereby to provide associated operational condition indication signals; and control means so responsive to such signals as to cause independent corresponding variation of the operational conditions of the relevant winch assembly; and in which said reference pressure levels include one characteristic of a predetermined difference in the lengths of the cables, wires or the like payed-out by the winch assemblies, and in which means are provided for producing a signal related to the actual difference in the amounts of cables, wires or the like payed-out, said control means being so responsive to the length difference reference level and said actual length difference as to produce an alarm or other indication of the condition that the amounts of the cables payed-out by the winch assemblies has exceeded a predetermined level. 
     
     
       6. A control system for controlling hydraulically operated winch assemblies whose cables, wires or the like are intended to be connected with the same trawl or other form of net used for sea fishing or for use with other objects or in situations in which it is required to maintain predetermined tensions in the cables, wires or the like, the control system including means for enabling a number of reference pressure levels each indicative of a particular required operational condition for the cables, wires or the like; such as paying-out, continuous pull, hauling-in; separate means for monitoring the operational conditions of the winch assemblies; means for comparing the results of the monitoring with an associated one of said reference pressure levels thereby to provide associated operational condition indication signals; and control means so responsive to such signals as to cause independent corresponding variation of the operational conditions of the relevant winch assembly; and in which said reference pressure levels include one characteristic of a predetermined difference in the lengths of the cables, wires or the like payed-out by the winch assemblies, and in which means are provided for producing a signal related to the actual difference in the amounts of cables, wires or the like payed-out said control means being so responsive to the length difference reference level and said actual length difference as to produce an alarm or other indication of the condition that the amounts of the cables payed-out by the winch assemblies has exceeded a predetermined level; said control system further comprising interference response means responsive to interference to a required movement of the common object of the interference responsive means including means for enabling paying-out of a predetermined additional length of cables, wires or the like means for detecting whether the interference still persists following the pay-out of the additional length of the cables wires or the like and for arresting any such additional pay-out thereby to permit the tension conditions in the cables, wires or the like to increase to a predetermined higher level to enable application of increased force on the object connected thereto for the purposes of attempting forcibly to free the said object from the interference; and means for causing adjustment of the control means to allow further paying-out of the cable, wire or the like if said interference still persists so as to prevent said higher level being exceeded, and to provide an alarm signal indicative that the predetermined higher level had been attained and that the interference still persists. 
     
     
       7. A method of controlling hydraulically operated winch assemblies whose cables, wires or the like, are intended to be connected with trawls or other forms of net used for sea fishing or for use with other objects or in situations in which it is required to maintain predetermined tensions in the cables, wires or the like, during the operation or use of the winch assemblies; the method including the steps of defining for each winch assembly a number of operational states including those characteristic of tension conditions acceptable in the cables during the operations of paying out, continuous pull, heaving in; establishing for each operational state a reference pressure level which is characteristic of the tension produced in the associated cable, wire or the like when the winch assembly thereof is operating at the selected operational state; separately monitoring during operation of the winch assemblies the instantaneous tensions; separately comparing for each winch assembly the instantaneous tension with the relevant reference pressure level applicable to the operational state required for that winch assembly to provide for each such comparison a control signal charcteristic of any difference between the instantaneous tension and the relevant pressure level; using the control signals to control means for separately adjusting the operational state of the associated winch assembly such that the instantaneous tensions are independently adjusted to maintain the required predetermined relationship between the cable, wires or the like, such method also including the steps of setting a reference pressure level characteristic of a predetermined difference in the length of the cables, wires or the like payed-out by the winch assemblies; monitoring the amounts of cables, wires or the like payed-out at any instant by each winch assembly; producing further control signals related to the difference in the amounts of cables, wires or the like payed-out; and using these further control signals to produce an alarm or other indication of the condition that the difference in the amount of the cables, wires or the like payed-out has exceeded a predetermined level. 
     
     
       8. A method as claimed in claim 7, and in which the method further includes the steps of detecting when any interference to the movement of the trawl, object of the like causes the normally acceptable continuous pull tension in the cables to start to exceed a relevant maximum acceptable pressure level, and following said detection causing operation of the winch assemblies to pay-out further predetermined lengths of cable; additionally ascertaining whether or not the additional cable payed-out leads to the removal of the interference and thus a reduction in the instantaneous cable tensions to values less than the relevant maximum acceptable reference pressure level; and producing an indication in the event that the tension continues to remain greater than the relevant reference condition. 
     
     
       9. A method as claimed in claim 8, in which following the pay-out of the additional lengths of cable and the production of said indication the instantaneous cable tensions are allowed to increase above the normally acceptable maximum pressure level to a predetermined excess level thereby to enable an increased pulling force to be exerted upon the trawl or other object being towed by the cables for the purposes of attempting to free the trawl or other object from the interference; separately monitoring the instantaneous in the cables to produce signals characteristic of such tensions and comparing such signals with signals related to the excess pressure level; allowing one of the instantaneous cable tensions to attain the excess level and when such condition is attained causing the control means for the winch assemblies to be operated to allow further pay-out of the cables to avoid the said excess tension from being exceeded and at the same time producing an alarm indication to the effect that the excess tension condition has been attained and that cable is being payed-out because of a sustained interference condition. 
     
     
       10. A method as claimed in claim 7, in which the initial stages of the paying-out and the later stages of the hauling-in are under manual control, and in which there is an automatic change-over between manual control and non-manual control by comparison of instantaneous cable tensions with a reference level indicative that a predetermined amount of cable is payed out from the winch assemblies.